docs: def addmag(self, magval):
          """Add a scalar magnitude to existing flux values.
  
          .. math::
  
              \\textnormal{flux}_{\\textnormal{new}} = 10^{-0.4 \\; \\textnormal{magval}} \\; \\textnormal{flux}
  
          Parameters
          ----------
          magval : number
              Magnitude value.
  
          Returns
          -------
          sp : `CompositeSourceSpectrum`
              New source spectrum with adjusted flux values.
  
          Raises
          ------
          TypeError
              Magnitude value is not a scalar number.
  
          """
          if N.isscalar(magval):
              factor = 10**(-0.4*magval)
              return self*factor
          else:
              raise TypeError(".addmag() only takes a constant scalar argument")